Some people may also have ringing in their ears tinnitus or dizziness. This increase in blood flow results in a firmer, longer-lasting erection. The most common side effects of VIAGRA: headache; flushing; upset stomach; abnormal vision, such as changes in color vision such as having a blue color tinge and blurred vision; stuffy or runny nose; back pain; muscle pain; nausea; dizziness; rash. Men may take it socially with other drugs, rather than for treatment of a medical condition. It’s available in 25 mg, 50 mg, and mg tablets and lasts up to 18 hours. If it is not treated right away, priapism can permanently damage your penis sudden vision loss in one or both eyes. Recreational ED drug use can even cause “psychogenic erectile dysfunction”.This medicine is Blue, Round Tablet Imprinted With “8 8”. Blue Round 8 8 – Sildenafil Citrate mg Tablet. CHOOSE BRAND-NAME VIAGRA The original little blue pill prescribed by doctors for over 20 years Clinically proven to treat men with erectile dysfunction (ED) Ongoing . If you experience chest pain, dizziness, or nausea during sex, seek immediate medical help. Sildenafil, Tadalafil, and Vardenafil can cause serious side effects. Read more. .